linux-kernel - Re: [PATCH net-next V7 01/14] documentation: networking: add shared devlink documentation

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20260203190105.2cc28e71@kernel.org>
Date: Tue, 3 Feb 2026 19:01:05 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Jiri Pirko <jiri@...nulli.us>
Cc: Tariq Toukan <tariqt@...dia.com>, Eric Dumazet <edumazet@...gle.com>,
 Paolo Abeni <pabeni@...hat.com>, Andrew Lunn <andrew+netdev@...n.ch>,
 "David S. Miller" <davem@...emloft.net>, Donald Hunter
 <donald.hunter@...il.com>, Jonathan Corbet <corbet@....net>, Saeed Mahameed
 <saeedm@...dia.com>, Leon Romanovsky <leon@...nel.org>, Mark Bloch
 <mbloch@...dia.com>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-doc@...r.kernel.org, linux-rdma@...r.kernel.org, Gal Pressman
 <gal@...dia.com>, Moshe Shemesh <moshe@...dia.com>, Carolina Jubran
 <cjubran@...dia.com>, Cosmin Ratiu <cratiu@...dia.com>, Jiri Pirko
 <jiri@...dia.com>, Randy Dunlap <rdunlap@...radead.org>, Simon Horman
 <horms@...nel.org>, Krzysztof Kozlowski <krzk@...nel.org>
Subject: Re: [PATCH net-next V7 01/14] documentation: networking: add shared
 devlink documentation

On Tue, 3 Feb 2026 10:18:22 +0100 Jiri Pirko wrote:
> Tue, Feb 03, 2026 at 04:40:23AM +0100, kuba@...nel.org wrote:
> >There needs to be a note here clearly stating the the use of "shared
> >devlink instace" is a hack for legacy drivers, and new drivers should
> >have a single devlink instance for the entire device. The fact that
> >single instance is always preferred, and *more correct* must be made
> >very clear to the reader. Ideally the single instance multiple function
> >implementation would leverage the infra added here for collecting the
> >functions, however.  
> 
> How exactly you can have a single devlink instance for multiple PFs of a
> same device? I don't really understand how that could work, considering
> dynamic binds/unbinds of the PFs within single host and/or multiple VMs
> passing PFs to.

The same way you currently gather up the devlink instances to create
the shared instance.

> >> +The implementation uses:
> >> +
> >> +* **Faux device**: Virtual device backing the shared devlink instance  
> >
> >"backing"? It isn't backing anything, its just another hack because we
> >made the mistake of tying devlink instances to $bus/$device as an id.
> >Now we need a fake device to have an identifier.  
> 
> Okay. I originally wanted to use an id, similar to what we have in
> the dpll. However I was forced by community to tie the instance to
> bus/device. It is how it is, any idea how to relax this bond?

Interesting! I was curious to research how we ended up here, found this:
https://lore.kernel.org/netdev/20160225225803.GA2191@nanopsycho.orion/
My reading is that Hannes was arguing against the _NAME attribute but
both _NAME and _INDEX were deleted? I think there's nothing wrong with
an index.

FWIW using devlink day to day, the bus/device is not at all useful as
an identifier. Most of code touching devlink at Meta either matches
on devlink dev info or assumes there's one instance on the system.

> >> +Similarly to other nested devlink instance relationships, devlink lock of
> >> +the shared instance should be always taken after the devlink lock of PF.  
> >
> >of an instance, not a PF  
> 
> lock of PF devlink instance. I think that is what the text says, no?

Sorry, I was trying to flag that using PF is not necessary great cause
we may support this on other functions in the future.